Determining the exact location of a device or person has increasingly become important to drive location based systems and services. Several technologies for doing so have resulted from efforts aimed at determining a person's location. For example, satellite-based global positions systems (GPS) provide location based services, provided the person with the device (i.e., receiver) is outdoors. While most of these technologies work well outdoors, they are inaccurate, indoors.
In particular, GPS systems do not work well indoors. In these systems, satellites broadcast signals to enable GPS receivers (i.e., smartphones, mobile devices, etc.) on or near the Earth's surface to determine location and synchronized time. Several factors, however, damage the GPS signal and thus affect accuracy.
For example, signal degradation occurs when the GPS signal is reflected off objects such as tall buildings or large rock surfaces before it reaches the receiver. This increases the travel time of the signal, thereby causing errors.
In addition, buildings, terrain, electronic interference, or sometimes even dense foliage can block signal reception, causing position errors or possibly no position reading at all. Thus, GPS units typically will not work indoors, underwater or underground. Accordingly, there is a need for improved techniques to determine the location of a device or person where standard GPS fails indoors.